Watch David Loyn's report from Islamabad

Pakistan was condemned by the international community for carrying out a sixth nuclear test on Saturday. India has carried out five explosions.

Mr Khan said the biggest nuclear explosion in the tests came from a boosted fission device which had twice the force of the bomb dropped on Hiroshima.

The scientist explains what kind of nuclear device was tested

The other five devices were smaller and he said designed for rapid transition into nuclear weapons. Pakistan, he said, is now in a position to make nuclear warheads should the need arise.

"We just want to see this kind of security on the safety of our country that it won't take us months, it won't take us weeks it can be done very quickly."

Abdul Qadir Khan says Pakistan's nuclear device is twice the size of the Hiroshima bomb

Explaining initial confusion over the latest round of tests on Saturday, Mr Khan said that the original plan had been to conduct two tests, but at the last minute the prime minister changed his mind, without telling the foreign minister.

"There are certain things the prime minister wants to keep to himself," Mr Khan said.

Mr Khan denied that one nuclear device remains unexploded beneath the ground.

He was speaking after returning with his colleagues from the testing sites in Baluchistan to a hero's welcome in the capital Islamabad.

Hundreds of people cheered them and threw flower petals in the air at Islamabad International airport.

Asked whether he had made something so dangerous that it should never have been created, the scientist replied that it was the West who had created the bomb and Pakistan had to test in the face of Indian aggression.

"I didn't create it. Those people who are supposed to be the champions and fathers of civilisation and human rights created it," he said.

An opinion poll has indicated that 97% of Pakistanis support their government's decision to conduct the nuclear tests.

Indian diplomat assaulted

Meanwhile, the Indian Government says one of its officials has been attacked in Islamabad.

An Indian Government spokesman said the attack on Mr BS Rawat was entirely unacceptable, and the Pakistani High Commissioner in Delhi had been summoned to receive a protest. Pakistan has not yet commented on the alleged incident.

A foreign ministry spokesman in Delhi said the official had been accosted and badly beaten up in front of his diplomatic residence.

Police in Indian-administered Kashmir say that a relative of a former junior minister in the federal government, Maqbool Dar, has been shot dead in the Anantnag district, and his brother abducted.

Kashmir is the subject of a long-standing territorial dispute between India and Pakistan.